A Five Percenter, he is serving time for murdering a man who laughed at him during a dice game. He often preaches Five Percenter philosophy while simultaneously dealing drugs. It is revealed that Supreme is responsible for the incarceration of Augustus Hill, having revealed Hill's location to the police after they picked him up on an old arrest warrant. As a result, Burr Redding, Augustus' stepfather, hates Allah. Despite his numerous enemies, lack of real allies, and his controversial and occasionally contradictory beliefs, Supreme survives numerous murder attempts, though he is killed eventually. It is possible that Ketchum's character and religion are a reference to Kenneth "Supreme" McGriff, a Five Percenter who ran the New York City based Supreme Team drug organization.

Supreme arrives in prison sponsored by Kareem Said. He is viewed as a threat by the Muslims since he preaches things that are as corrupting as they are enhancing. Rooming with Poet, he finds himself an ally to Simon Adebisi and the Homeboys. Since the Muslims are being led by Zahir Arif, Supreme claims Arif is nothing more than a "Kareem Said wannabe" he attempts to convert a few members such as Nacim Bismilla. When Arif asks Adebisi to kill Supreme, Supreme and the other Homeboys tell Arif to watch where he walks. Being on Adebisi's good side while Oz is under the management of Martin Querns, Supreme is having a good time in Em City, not worrying about anything for the most part. Querns even names him and Poet trustees when the Italian and Latino inmates are transferred out of Em City.

Supreme informs the black inmates (mainly Leroy Tidd and Mondo Browne) that they are being outsold in drugs by Jamaican inmate Desmond Mobay whom he and Adebisi don't fully trust. This situation builds into tension between Supreme and Browne. Adebisi steps in to stop them from fighting. With only a few white inmates left in Em City, Ryan O'Reily and Chris Keller (both white) conspire to disrupt Querns' system. They first murder Nate Shemin and then Mondo Browne. They successfully frame Supreme for the murders by planting Supreme's necklace at the scene and the murder weapon in Supreme's pod. The evidence is enough for Querns, who allows Supreme to be beaten by Adebisi and the all black correctional officers for ending Quern's streak of no violence. Supreme is sent to isolation and will stand trial for two counts of murder.

Supreme Allah is released from isolation after it is determined there is not enough evidence to convict him of murder. While in the hole, he figures out that Keller and O'Reily set him up and he warns the two of them that they will pay for framing him. Meanwhile Burr Redding tells Augustus Hill that Supreme told the cops where he was the night he got arrested to avoid going to jail himself. Furious, Hill attacks Supreme Allah in the shower and is thrown out of his wheelchair and beaten by Supreme instead. Furious that Supreme assaulted Augustus, Burr Redding calls in Tug Daniels. Daniels' older brother was murdered by Supreme and Redding will give him a spot in the gang if he murders him. In the visiting room, Supreme is talking to his girlfriend explaining how he was unjustly sent to isolation when Tug Daniels approaches with a shank supplied by Poet and stabs him. Supreme goes to the hospital and Daniels is charged with attempted murder. In the hospital Supreme is attacked by inmate Omar White who is stopped by the S.O.R.T. team. Earlier when he was initially dismissed by Redding, Chucky Pancamo, leader of the Italians, and Enrique Morales, leader of the Latinos, approach Supreme. Looking for a way to kill Redding, they offer him a third in the drug trade if he kills Burr Redding. Supreme agrees after he getting support from other black inmates.

When released from the hospital, he formulates a plan to eliminate Redding using Augustus Hill. Hill has been ostracized by Burr for alerting the S.O.R.T. team about White's plan to kill Supreme. He befriends Hill, telling him that he is sorry for snitching on him and that he is the best ally to have now that he has survived two murder attempts. Augustus does not fully trust Supreme though and does not initially go along with him. Supreme is also plotting with Tug Daniels, who has decided Supreme is a worthy ally after surviving the stabbing. In this plan, Supreme will pretend to work with Pancamo and Morales while Tug will pretend to work with Redding. A spy of Redding's, a marine colonel in Oz, informs Burr of the plot, so Burr has Poet rent the gym from the COs to kill Tug Daniels. After this happens, Pancamo and Morales tell Supreme to hurry up and kill Redding. Growing frustrated, Supreme takes a shank and attempts to stab Redding in the cafeteria but is stopped by Augustus. Augustus, desperate to save Burr, pays Christian inmate Harden to steal Supreme's medical records. He finds out Supreme is fatally allergic to eggs and tells Poet. The Homeboys and O'Reily fill his food with eggs and Supreme Allah dies from Anaphylaxis at the lunch table next to Augustus. Burr then forgives Hill and allows him to be an ally of the Homeboys again.